Photoresist masks are commonly used in the semiconductor industry to pattern materials such as semiconductors or dielectrics. For example, photoresist masks are used in a dual damascene process to form metal interconnects during the back end of line (BEOL) metallization of a semiconductor device. The dual damascene process involves formation of a photoresist mask on a dielectric layer overlying a metal contact structure or metal conductive layer, such as a tungsten layer. The dielectric layer is then etched according to the photoresist mask to form a via and/or trench that expose the underlying metal contact structure or metal conductor layer. The via and trench, collectively known as a dual damascene structure, are typically defined using two lithography steps. After the lithography steps are performed, the photoresist mask is removed from the dielectric layer before a conductive material is deposited into the via and/or trench to form an interconnect.
As scaling of semiconductor devices continues, it becomes more difficult to achieve the necessary critical dimensions for vias and trenches. Thus, metal hardmasks are increasingly used to provide better profile control of vias and trenches. The metal hardmasks are typically made of titanium (Ti) or titanium nitride (TiN). A wet etching process is normally performed after forming the via and/or trench of the dual damascene structure to remove the metal hardmask. In the conventional process, it is desirable that the wet etching process use an etchant chemistry that effectively removes the metal hardmask without affecting the underlying metal conductor/barrier layers and dielectric material. In other words, the etchant chemistry is required to etch the metal hardmask at a much faster rate than it etches the metal conductor/barrier layers and dielectric layer.
However, titanium nitride is commonly used as both a metal hardmask and as a barrier metal, such as for tungsten contacts, in metal contact structures. Therefore, it may be difficult or impossible to use a wet etchant to selectively remove titanium nitride hardmasks after performing a dual damascene process that exposes a metal contact structure including a titanium nitride barrier metal. Specifically, the etchant will attack and form voids in the metal contact structure during removal of the metal hardmask. Alternatively, the same metals cannot be used for the metal hardmask and in the metal contact structure.
Accordingly, it is desirable to provide integrated circuits and methods for fabricating integrated circuits with improved contact structures. In addition, it is desirable to provide improved integrated circuits and improved methods for fabricating integrated circuits that inhibit etching of contact structure barrier layers during removal of hardmasks. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.